1. Field of the Invention The present invention relates generally to the conversion of electric signals. More specifically, the present invention relates to a signal conversion circuit for converting Non-Return to Zero Level Data to Bi-Phase Data.
2. Description of the Prior Art
Telemetry data transmitted from a missile to a ground station generally requires that the data be converted from a Non-Return to Zero Level (NRZ-L) data format to a Bi-Phase data format.
In the past this data conversion was performed by an EXCLUSIVE NOR circuit which converted incoming NRZ-L data to Bi-Phase data and which is defined by the following Boolean logic expression. EQU X.sub.0 = CLK .sym.DATA (1)
where X.sub.0 is the Bi-Phase output signal, CLK is the input clock signal and DATA is the incoming NRZ-L data. As is evident from FIG. 2D utilizing a conversion circuit defined by Expression (1) to convert incoming NRZ-L data to Bi-Phase data results in a waveform which includes undesirable spikes. These undesirable spikes occur whenever a data bit (illustrated in FIG. 2C) changes state from a logic one state to a logic zero state or from a logic zero state to a logic one state.
These undesirable spikes need to be eliminated which would require, for example, a filter circuit to be connected to the output X.sub.0 of the circuit define by Expression (1). However, a filter circuit may not entirely eliminate spikes from the Bi-Phase data signal of FIG. 2D, resulting in noise in the Bi-Phase data signal of FIG. 2D.
It is also very desirable to eliminate spikes and unwanted noise when Non-Return to Zero Level (NRZ-L) to Bi-Phase data is used in conjunction with a frequency modulated (FM) recorder.
Accordingly, it is an object of the present invention to provide an improved signal conversion circuit for converting incoming NRZ-L data to Bi-Phase data.
It is another object of the present invention to provide a signal conversion circuit for eliminating undesirable spikes from NRZ-L data which is being converted to Bi-Phase data.
It is still another object of the present invention to provide a relatively simple in design, economical and highly efficient signal conversion circuit for eliminating undesirable spikes from NRZ-L data which is being converted to Bi-Phase data.
Various other advantages and novel features of the signal conversion circuit constituting the present invention will become apparent to those skilled in the art as a more detailed description of the present invention is set forth below.